Doesn't really seem a legal issue to me. There have been many legal battles over the years over band names (Beach Boys, Pink Floyd, Little River Band), but I don't hear anyone else claiming Crowded House.
Look, I don't always like line-up changes, and totally understand the feeling on this board, particularly in regards to Mark, but line-ups do change. And it IS Neil's band, no matter what anyone says.
Just enjoy having new Neil music, no matter how he deigns to brand it.